The candidate for this NINDS K25 Mentored Quantitative Research Career Development Award was trained as a biomedical engineer and has performed experimental and modeling research on clinical neuroprostheses and on applications of spinal neurophysiology discoveries to neuroprosthetic problems. The mentor is a leader in the field of neural plasticity and regeneration. The candidate's long term objective is to further the understanding of the motor program coded at the spinal level, and its functional application. Short term career goals are to develop an understanding of the effects of neural plasticity on spinal circuits that produce organized force patterns at the limb's effector when electrically/pharmacologically activated. Such an understanding would contribute to the development of devices combining neuroprostheses enhanced by sensorimotor training and regenerated spinal pathways. The proposed career development plan includes specific training in neural plasticity, histological and electrophysiological methods. The specific aims of the research plan are to examine how spinal cord injuries, sensorimotor rehabilitation, and neural transplants affect the operation of the spinal circuits. The plan is an innovative integration of the candidate's engineering-based neuroprosthetics research interests with the mentor's long term interests in spinal repair. Three projects are proposed. The first looks at the effects of chronic spinalization on the force pattern structure produced by electrical activation of dorsal/medial regions of the cat's spinal lumbar enlargement. The second project examines the effects of locomotor training on the spinal animal's walking abilities and spinal circuitry organization. The third project proposes to extend transplantation protocols developed in the rat to the cat model, and to identify the functional benefits provided by these spinal grafts when combined with locomotor training. Upon completion of the locomotor training, the force patterns coded into the neuronal circuit of the spinal cord are investigated via intraspinal microstimulation. The results will extend our knowledge of the effects of neural plasticity on portions of the spinal circuitry with potential for neuroprosthetic applications. Furthermore, the results will demonstrate the cross-species application of a neural graft, as well as the effect of sensorimotor training on the regenerated pathways.